Hey @swanseasharks - welcome to the OpenRent Community!
Yes, there’s no need to renew and sign onto another fixed term if you don’t want to.
It might be sensible to sign a new fixed term, however, since this gives both you and the tenants the security that the tenancy will continue to run at least to the agreed end-date.
In a periodic ‘rolling’ tenancy, the tenants could move out with just a month’s notice, which could lead to a void period if you can’t find replacements quickly enough.
If you’re a Rent Now landlord, then you can simple renew your contract through the OpenRent dashboard, for free!